Merrill,
F. J. H., Dry concentration of placer gold: Min. and Sci. Press, vol.
105, 11)12. pp. 50-52. Latest and most complete summary of subject.
Mining Magazine. Precis of technology; dry concentration of placer gold, vol. 7, 1912, pp. 148-149. Resume1 of article by same title of F. J. H. Merrill cited above.
Peterson,
G. M., Dry placer machines: Min. and Sci. Press, vol. 191, 1910, p.
639. Describes Quinner pulverizer and Stebbins concentrator.
Richards,
J. V., Dry washing for placer gold in Sonora, Mexico: Trans. Am. Inst.
Min. Eng., vol. 41, 1911, pp. 797-802. Describes operations of ': dry washing " machines and Quinner pulverizer.
Wilson, E. B., Dry placer mining machines: Mines and Minerals, vol. 31, 1911, p. 589.
DRY AND SILICEOUS ORES.
In
1911 dry and siliceous ores, including true gold ores and precious
metal bearing ores not classed as copper, lead, or zinc ores, produced
$66,369,199 in gold, against an output from this source of $65,313,092
in 1910. States producing over $1,000,000 from these ores in 1911
ranked as follows: Colorado, Nevada, California, South Dakota, Alaska,
Montana, Arizona, and Utah, or in the same relative order as in 1910
and 1909.
Considerably
increased output from this source was recorded for 1911 from South
Dakota and Utah, and decreases are found from Colorado and Nevada.
The
siliceous ores are in part free-milling (amalgamating), as in Alaska,
California, and Oregon; in part both amalgamating and concentrating,
as in many States; in smaller part simply concentrating ores, as in
parts of Colorado and Arizona; or smelting ores. Tailings both from old
dumps and from present milling are largely reworked by concentration
and subsequent cyanidation. The all-sliming cyanida-tion method is also
of increasing importance, and crushing is now largely by tube mills as
well as by stamp and gyratory mills.
The
loss in tailings from gold mills is being constantly cut down and the
most serious present loss is in tailings from concentrating plants. The
chlorination process is of decreasing relative importance. Smelting is
mainly of concentrates and of siliceous and pyritic ores which are also
valuable as fluxes. Exact figures of relative output by methods have
already been briefly given and will appear in detail by States in
another table.
COPPER ORES.
The
production of gold from copper ores in 1911 was $5,450,079, against
$5,471,200 from this source in 1910. Increases in gold output from
these ores are noted for 1911 from Alaska, Idaho, Nevada, New Mexico,
and Utah, and decreases from most of the other copper-producing
States, notably California. The States leading in output of gold from
these ores are Utah (predominantly) and Arizona (each with an output of
over $1,000,000 from this source), and Montana, Nevada, and California,
all in the order named. The gold is recovered by electrolytic refining
of blister copper obtained in smelting crude ores and concentrates.
LEAD ORES.
The
output of gold from lead ores in 1911 was $1,201,606, against a
production from this source of $1,122,090 in 1910. The Utah lead ores
rank first in total yield of gold, followed by those from Colorado. The
remainder of gold from this source is chiefly from Arizona, Idaho, and
Montana, in the order named. Increases in 1911 are noted from Arizona,
Colorado, and Idaho, and decreases from most of the other States.
